// Test page one: Create image + Session
session_start();
function randomString() {
    $string = "abcdefghijklmnopqrstuvxyz1234567890";

    $final = "";
    for($i=0;$i<=7;$i++) {
        $number = rand(1, 35);
        $getString = substr($string, $number, 1);
        $final .= $getString;
}

    return $final;
}

$_SESSION['CaptchaImage'] = randomString();
$CaptchaImage = $_SESSION['CaptchaImage'];

function createImage($randomString) {
    header ('Content-Type: image/png');
    $getImage = imagecreatetruecolor(80,20);
        $colorBackground = imagecolorallocate($getImage, 0, 0, 0);
        $colorString = imagecolorallocate($getImage, 125, 125, 125);
        $fontImage = imagestring($getImage, 2, 5, 5, $randomString, $colorString);
    $showImage = imagepng($getImage);
    $showImage = imagedestroy($getImage);

    return $showImage;
}
createImage($CaptchaImage);


// Test page two: Show and test image

session_start();

if($_GET['do'] == "") {
    echo "<img src='sites/test.php'>";
} else {

if($_GET['do'] == $_SESSION['CaptchaImage']) {
    echo "The Captcha is correct!";
} else {
    echo "The Captcha is incorrect!";
}
}